The aim of this article was to determine trends in infant mortality and related risk factors in Porto Alegre, Rio Grande do Sul State, Brazil. The study was based on data from a live birth and infant death registry for the years 1996 to 2008. Times trends were analyzed for overall and partial infant mortality rates according to maternal schooling, number of prenatal visits, maternal age, number of live and dead children, sex of the newborn, type of delivery, birth weight, and type of hospital. Poisson regression was used to estimate the influence of socioeconomic status and other risk factors. The infant mortality rate dropped among mothers with less than 11 years of schooling. There were no significant changes among newborns of mothers with 12 or more years of schooling. Maternal socioeconomic status was the factor most closely associated with the reduction in infant mortality. Still, the downward trend failed to achieve its full potential, due to the increase in low birth weight.